A terahertz vortex phase plate based on a dual-band staggered metasurface

Abstract

The present invention relates to the field of optical device technology, and in particular to a terahertz vortex phase plate based on a dual-band staggered metasurface. The metasurface is composed of a number of periodically arranged metasurface units, and each metasurface unit is composed of a metal structure layer, an intermediate dielectric layer, and a metal reflective layer from top to bottom; the metal structure layer includes two concentrically arranged metal opening rings, and the rotation angles of the two metal opening rings are controlled to generate vortex beams with different topological charges at different frequencies, and the electromagnetic coupling between the two metal opening rings is controlled to achieve phase control at different frequency bands based on a single rotation of each metal opening ring. The phase plate of the present invention has a simple and thin structure, which is convenient for integrated installation while reducing costs. Secondly, without introducing phase change materials, it can realize independent control of terahertz waves in two different frequency bands, meet the generation requirements of multi-modal vortex beams, and improve spectrum utilization.

Description

Technical Field

[0001] The present invention relates to the technical field of optical devices, and in particular to a terahertz vortex phase plate based on a dual-band staggered metasurface. Background Art

[0002] Terahertz waves, a band in the electromagnetic spectrum with frequencies higher than microwaves and lower than visible light, possess superior properties such as broadband, high resolution, low energy, high penetration, and transient properties. They possess significant application value in both cutting-edge scientific research and industrial technology. In recent years, terahertz wave generation technology has played an increasingly important role in research on charge carrier dynamics, excitation of superconducting states in materials, coherent phonon dynamics, all-optical electron beam acceleration, biomolecular structural dynamics, and quantum state manipulation.

[0003] A vortex beam is a beam with a spiral optical phase structure. Its phase distribution has potential applications in emerging fields such as high-resolution terahertz imaging, electron acceleration, and quantum state manipulation. Currently, the main methods for generating terahertz vortex waves include holography, spiral phase plates, and metasurfaces. Holography is widely used, but its implementation is complex and there is a lack of mature spatial modulators in the terahertz band. Spiral phase plates have a narrow operating band and large thickness, resulting in inconsistent vortex beam quality at different frequencies. Metasurfaces are two-dimensional artificial structures composed of periodic or non-periodic units of subwavelength size. Compared with naturally occurring materials, they have superior electromagnetic control capabilities and are conducive to the generation of vortex waves.

[0004] However, existing terahertz vortex phase plates still have the following defects:

[0005] (1) Most optical devices cannot be directly used in terahertz systems due to the high loss of their materials in the terahertz band. Therefore, it is necessary to select appropriate materials and processes to manufacture terahertz devices.

[0006] (2) In recent years, most devices that generate terahertz vortex beams are limited to topological charges of 1 or 2. The technology to increase the topological charge of terahertz vortex phase plates is relatively difficult, and there is little research on terahertz vortex beam control devices with larger topological charges (l ≥ 3).

[0007] (3) The use of transmissive metasurfaces to generate terahertz vortex beams has the problem of low transmittance, resulting in low working efficiency;

[0008] (4) Most existing terahertz vortex phase plates can only generate terahertz vortex beams at a single frequency and cannot generate vortex beams in multiple frequency bands without structural modification or the introduction of phase-change materials. Therefore, finding a terahertz vortex phase plate that can efficiently generate high-order topological charge terahertz vortex beams is a pressing technical challenge for those skilled in the art. Summary of the Invention

[0009] The present invention aims to improve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a terahertz vortex phase plate based on a dual-band staggered metasurface.

[0010] The technical solutions of the present invention are as follows:

[0011] A terahertz vortex phase plate based on a dual-band staggered metasurface, wherein the metasurface is composed of a plurality of periodically arranged metasurface units, each of which comprises, from top to bottom, a metal structure layer, an intermediate dielectric layer, and a metal reflective layer; wherein the metal structure layer comprises:

[0012] Two concentrically arranged metal open rings generate vortex beams with different topological charges at different frequencies by controlling the rotation angles of the two metal open rings respectively, and control the phase at different frequency bands based on a single rotation of each metal open ring by weakening the electromagnetic coupling between the two metal open rings.

[0013] In a possible technical solution, further, the metal open ring includes:

[0014] A first metal open ring is provided on the intermediate dielectric layer;

[0015] The second metal opening ring is arranged outside the first metal opening ring and has the same center as the first metal opening ring.

[0016] In a possible technical solution, further, by respectively controlling the rotation angles of the two metal split rings to generate vortex beams with different topological charges at different frequencies, specifically:

[0017] When the first metal split ring is rotated, a vortex beam with a topological charge of -1 is generated in the 1.35THz frequency band;

[0018] When the second metal split ring is rotated, a vortex beam with a topological charge of 3 is generated in the 0.47 THz frequency band.

[0019] In a possible technical solution, further, the first metal open ring has an opening angle range of 30° to 60°, an outer diameter of 21 μm to 25 μm, and an inner diameter of 16 μm to 20 μm.

[0020] In a possible technical solution, further, the second metal open ring has an opening angle range of 30° to 60°, an outer diameter of 46 μm to 50 μm, and an inner diameter of 41 μm to 45 μm.

[0021] In a possible technical solution, further, the arrangement period of the metasurface units is p=110 μm to 120 μm, wherein,

[0022] The thickness of the metal structure layer and the metal reflective layer is not less than 0.2 μm;

[0023] The thickness of the intermediate dielectric layer ranges from 75 to 125 μm.

[0024] In a possible technical solution, further, in each metasurface unit, the centers of the two metal open rings and the geometric centers of the intermediate dielectric layer and the metal reflective layer are all located on the same vertical line.

[0025] In a possible technical solution, further, the intermediate dielectric layer is polyimide, has a relative dielectric constant of 3.5, and a tangent loss in the range of 0.001 to 0.005.

[0026] In a possible technical solution, further, the metal structure layer and the metal reflective layer are made of the same material.

[0027] In a possible technical solution, further, the material is any one of gold, silver, copper, and aluminum.

[0028] The terahertz vortex phase plate based on the dual-band staggered metasurface of the present invention is composed of metasurface units periodically arranged in the same plane. By leveraging the metasurface's ability to modulate terahertz waves and rotating metal split rings separately, vortex beams can be generated in two different terahertz frequency ranges. While generating terahertz vortex beams with a larger topological charge (l ≥ 3), this approach also lays the foundation for subsequent research into terahertz vortex beam applications.

[0029] Compared with the existing technology, the terahertz vortex phase plate based on the dual-band staggered metasurface provided by the present invention has the following advantages:

[0030] (1) Small size, light weight, and high integration: The phase plate adopts metasurface technology, has a simple and thin structure, and is easy to integrate into complex optical or communication systems, while reducing manufacturing and use costs.

[0031] (2) Strong dual-frequency control and flexible control capabilities: Without introducing phase change materials, through the double-ring staggered structural design, the phase plate can independently control terahertz waves in two different frequency bands, meet the generation requirements of multi-modal vortex beams, and improve spectrum utilization.

[0032] (3) Potential for multi-scenario applications: This phase plate is not only suitable for the communication field, but can also be used in radar, high-resolution imaging, energy transmission and other scenarios, showing its wide application potential in the field of electromagnetic control.

[0033] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0035] Figure 1 Schematic diagram of the overall structure of the terahertz vortex phase plate based on the dual-band staggered metasurface of the present invention;

[0036] Figure 2 Schematic diagram of the structure of the metasurface unit;

[0037] Figure 3 Schematic diagram of the structural design of the metal structure layer of the metasurface unit;

[0038] Figure 4 Schematic diagram of the amplitude and phase of a circularly polarized wave incident on a simultaneously rotating metal layer structure according to an embodiment of the present invention;

[0039] Figure 5 Schematic diagram of the amplitude and phase of a circularly polarized wave incident on an open ring rotating outside a metal structure layer according to an embodiment of the present invention;

[0040] Figure 6 Schematic diagram of the amplitude and phase of a circularly polarized wave incident on an open ring rotating in a metal structure layer according to an embodiment of the present invention;

[0041] Figure 7 Schematic diagram of the far-field distribution of vortex waves generated by the rotation of the outer ring in an embodiment of the present invention;

[0042] Figure 8 Schematic diagram of the far-field distribution of vortex waves generated by the rotation of the inner ring in an embodiment of the present invention;

[0043] Figure 9 Schematic diagram of far-field beams generated by inner and outer ring rotations in an embodiment of the present invention;

[0044] Figure 10 Schematic diagram of the effect of different materials of the metal structure layer on performance in an embodiment of the present invention;

[0045] Figure 11 Schematic diagram showing the effect of dielectric layer thickness on performance in an embodiment of the present invention;

[0046] Figure 12 Schematic diagram showing the effect of the inner diameter and outer diameter of the first metal split ring on performance in an embodiment of the present invention;

[0047] Figure 13 Schematic diagram of the effect of the inner diameter and outer diameter of the second metal open ring on performance in an embodiment of the present invention.

[0048] Reference numerals:

[0049] 10. Metasurface unit;

[0050] 100, metal structure layer; 110, first metal open ring; 120, second metal open ring; 200, intermediate dielectric layer; 300, metal reflective layer. DETAILED DESCRIPTION

[0051] The embodiments of the present invention are described in detail below. The embodiments described with reference to the accompanying drawings are exemplary. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0052] It should be noted that when an element is referred to as being “fixed to” another element, it may be directly on the other element or there may be an intermediate element. When an element is referred to as being “connected to” another element, it may be directly connected to the other element or there may be an intermediate element.

[0053] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0054] In the specification, claims, and accompanying drawings of this application, the terms "first," "second," "third," and the like are used to distinguish different objects and are not used to describe a particular order. Furthermore, the terms "including," "comprising," "having," and any variations thereof are intended to cover non-exclusive inclusions. For example, a list of steps or elements may be included, or alternatively, steps or elements not listed may be included, or other steps or elements may be included that are inherent to the process, method, product, or apparatus.

[0055] Example 1

[0056] like Figures 1 to 9 As shown, this embodiment provides a terahertz vortex phase plate based on a dual-band staggered metasurface, wherein the metasurface is composed of a plurality of periodically arranged metasurface units 10, each of which is composed of a metal structure layer 100, an intermediate dielectric layer 200, and a metal reflective layer 300 from top to bottom, with no gaps between adjacent structure layers; wherein the metal structure layer includes:

[0057] The first metal opening ring 110 and the second metal opening ring 120 have the same center. The first metal opening ring 110 is arranged on the intermediate dielectric layer 200; the second metal opening ring 120 is arranged outside the first metal opening ring 110 and has the same center as the first metal opening ring 110. By controlling the rotation angle of the two metal opening rings respectively, vortex beams with different topological charges at different frequencies are generated. Specifically, when the first metal opening ring 110 is rotated, a vortex beam with a topological charge of -1 is generated in the 1.35THz frequency band; when the second metal opening ring 120 is rotated, a vortex beam with a topological charge of 3 is generated in the 0.47THz frequency band. By weakening the electromagnetic coupling between the two metal opening rings to achieve phase control at different frequency bands based on a single rotation of each metal opening ring, specifically by rotating one of the metal opening rings alone and keeping the other metal opening ring stationary, the phase of a specific frequency point can be independently and precisely controlled.

[0058] It should be noted that the opening angle β of the first metal opening ring 110 is in the range of 30° to 60°, the outer diameter r2 is 21μm to 25μm, and the inner diameter r1 is 16μm to 20μm. The opening angle of the second metal opening ring 120 is in the range of 30° to 60°, the outer diameter r4 is 46μm to 50μm, and the inner diameter r3 is 41μm to 45μm. Preferably, in this embodiment, the outer diameter r2 of the first metal opening ring 110 is 23μm, the inner diameter r1 is 18μm, the opening angle of the first metal opening ring 110 is 30°, the outer diameter r4 of the second metal opening ring 120 is 48μm, the inner diameter r3 is 43μm, and the opening angle of the second metal opening ring 120 is 30°. Figure 3 shown.

[0059] It should be noted that the arrangement period of the metasurface units 10 is p=110 μm to 120 μm, wherein:

[0060] The thickness of the metal structure layer 100 and the metal reflective layer 300 is not less than 0.2 μm;

[0061] The thickness of the intermediate dielectric layer 200 ranges from 75 to 125 μm. In this embodiment, the thickness of the metal structure layer 100 and the metal reflective layer 300 are both 0.2 μm. The arrangement period of the metasurface unit 10 is p=110 μm, and the thickness t1 of the intermediate dielectric layer 200 is 100 μm.

[0062] It should be noted that, in each metasurface unit 10 , the centers of the two metal open rings and the geometric centers of the intermediate dielectric layer 200 and the metal reflective layer 300 are all located on the same vertical line.

[0063] It should be noted that the intermediate dielectric layer 200 is made of polyimide, has a relative dielectric constant of 3.5, and a loss tangent in the range of 0.001 to 0.005.

[0064] It should be noted that the metal structure layer 100 and the metal reflective layer 300 are made of the same material. The material is any one of gold, silver, copper, and aluminum. In this embodiment, the metal structure layer 100 and the metal reflective layer 300 are both made of copper, with a thickness of 0.2 μm and an electrical conductivity of 5.8×10 7 Different material selections may have corresponding effects on device performance, which is also within the scope of protection of the present invention.

[0065] The terahertz vortex phase plate of this embodiment is subjected to simulation test:

[0066] like Figures 4 to 6 As shown, according to the principle of geometric phase (PB phase), for the incident circularly polarized wave, when the metal structure layer 100 rotates by an angle of When , the metasurface unit will obtain a phase increment twice the rotation angle, that is, By rotating the entire metasurface unit, the metasurface unit exhibits excellent PB phase characteristics in the frequency range of 0.2THz to 1.5THz. The amplitude of the cross-polarized wave when the circularly polarized wave is incident is almost unchanged, and the phase distribution and the rotation angle show Linear relationships, such as Figure 4 As shown, Figure 4 (a) is the amplitude distribution when the two rings rotate simultaneously. Figure 4 (b) in the figure is the phase distribution.

[0067] By effectively controlling the electromagnetic coupling between the two inner rings, the inner ring or outer ring can be rotated independently to precisely control the PB phase at a specific frequency. Specifically, when the first metal split ring 110 (i.e., the inner ring) remains stationary and the second metal split ring 120 (the outer ring) rotates at intervals of 22.5 degrees, at the frequency of 0.47 THz, the amplitude remains stable, while the phase shows a characteristic of a double-angle relationship and uniform distribution. This phenomenon is particularly evident in the Figure 5 It is intuitively demonstrated in Figure 5 (a) in is the corresponding amplitude distribution, Figure 5 (b) in the figure is the phase distribution. Similarly, when the second metal split ring 120 (outer ring) is fixed and the first metal split ring 110 (inner ring) rotates at intervals of 22.5°, the phase at the frequency of 1.35 THz also follows a doubled angle relationship and is evenly distributed, and the amplitude remains constant, as shown in the figure below. Figure 6 As shown, Figure 6 (a) in is the corresponding amplitude distribution, Figure 6 (b) in the figure is the phase distribution. The independent control mechanism of this embodiment not only significantly improves the control capability of the phase at a specific frequency point, but also provides a strong guarantee for the flexibility and accuracy of the metasurface structure in multi-band applications, thus expanding its application potential in related fields.

[0068] like Figures 7 and 8 As shown, in order to realize the vortex beam carrying orbital angular momentum (OAM), the metasurface unit 10 needs to be arranged according to a certain periodic law. The metasurface unit structure at different positions must satisfy the formula The phase distribution condition is is the topological charge number that produces OAM, is a given spatial coordinate. By rotating the inner and outer rings separately, the control of different topological charges at two different frequencies can be achieved simultaneously. Specifically, Figure 7The rotating outer ring structure was demonstrated, and a vortex beam with a topological charge of 3 was successfully formed in the 0.47THz frequency band. Figure 7 (a) in the figure is the amplitude distribution diagram. Figure 7 (b) is the phase distribution diagram, according to Figure 7 It can be seen that the amplitude and phase distribution of the rotating outer ring structure have a significant effect. Figure 8 It presents a rotating inner ring structure, generating a vortex beam with a topological charge of -1 in the 1.35THz frequency band, whose amplitude is almost zero at the center, forming a typical donut-shaped beam morphology, in which Figure 8 (a) in the figure is the amplitude distribution diagram. Figure 8 (b) is the phase distribution diagram. In this embodiment, the terahertz vortex phase plate based on the dual-band staggered metasurface is composed of 30×30 metasurface units with a size of 3300μm×3300μm. Therefore, the terahertz vortex phase plate based on the dual-band staggered metasurface of the present invention can generate vortex beams with different topological charges at different frequencies by respectively controlling the rotation angles of the two metal opening rings. In addition, it should be noted that according to the above formula, by changing the array arrangement, vortex beams with topological charges of 1, 2, 3 or -1, -2, -3 can be generated, which is also within the scope of protection of the present application.

[0069] Example 2

[0070] like Figure 9 As shown, based on the above embodiment, this embodiment can independently control the channel beams of two frequency points at the same time by rotating the inner ring and the outer ring at the same time. Specifically, the size of the metasurface unit array is 30×30. When the inner ring of the metasurface unit is arranged as all 0s, that is, when the phase response of all inner rings is the same, a single beam is formed at 1.37THz, as shown in FIG. Figure 9 As shown in (a); when the outer ring arrangement of the metasurface unit is 0 / 1, a dual beam is formed at 0.48 THz, as shown in Figure 9 This result demonstrates the dual-band misaligned metasurface's ability to independently control phase at two different frequencies, demonstrating its potential application in 6G multi-band compatible communications. By leveraging electromagnetic coupling between the two metal split rings, the phases at two different frequency bands can be controlled based on their independent rotation.

[0071] Example 3

[0072] like Figure 10As shown, based on the above embodiments, this embodiment analyzes the impact of different materials of the metal structure layer on the performance. When the materials of the two open rings of the metal layer are gold, silver, copper, aluminum and other metals, the amplitude of the polarization conversion remains almost unchanged, and different materials have little effect on its performance. The main source of influence on the performance is the different structural design and the thickness of the dielectric layer.

[0073] Example 4

[0074] like Figures 11 to 13 As shown in FIG, this embodiment verifies that the radius change of the metal structure layer ring and the thickness of the dielectric layer have a certain influence on the overall performance, such as Figure 11 As shown in Figure 1, when the thickness of the dielectric layer increases from 75μm to 125μm, the second peak near 0.3THz gradually weakens, and the peak near 1.3THz gradually strengthens and moves to low frequencies. Taking all factors into consideration, when the thickness of the dielectric layer is 100μm, the amplitude values ​​at 0.47THz and 1.37THz are greater than 0.8. When the inner diameter of the first metal open ring increases from 16μm to 20μm, as shown in Figure 1, Figure 12 As shown in (a), the amplitude changes little in the entire frequency band, and the radius of the first metal opening ring has a relatively weak effect on it. The outer diameter increases from 21μm to 25μm, as shown in Figure 12 As shown in (b), the distance between the two rings decreases, the coupling increases, and the peak-to-valley increases, but the amplitude at 1.37 THz remains unchanged. When the inner diameter of the second metal split ring increases from 41 μm to 45 μm, as shown in Figure 13 As shown in (a), the amplitude changes little in the entire frequency band, and only slightly changes around 0.3 THz. When the outer diameter increases from 46 μm to 50 μm, as shown in Figure 13 As shown in (b), the amplitude values ​​at 0.47 THz and 1.37 THz remain almost unchanged, and only the amplitude at 1.1 THz decreases. The main reason for this is the splitting caused by the strong coupling of the two rings.

[0075] The terahertz vortex phase plate based on the dual-band staggered metasurface of the present invention is composed of metasurface units periodically arranged in the same plane. By leveraging the metasurface's ability to modulate terahertz waves and rotating metal split rings separately, vortex beams can be generated in two different terahertz frequency ranges. While generating terahertz vortex beams with a larger topological charge (l ≥ 3), this approach also lays the foundation for subsequent research into terahertz vortex beam applications.

[0076] Compared with the existing technology, the terahertz vortex phase plate based on the dual-band staggered metasurface provided by the present invention has the following advantages:

[0077] (1) Small size, light weight, and high integration: The phase plate adopts metasurface technology, has a simple and thin structure, and is easy to integrate into complex optical or communication systems, while reducing manufacturing and use costs.

[0078] (2) Strong dual-frequency control and flexible control capabilities: Without introducing phase change materials, through the double-ring staggered structural design, the phase plate can independently control terahertz waves in two different frequency bands, meet the generation requirements of multi-modal vortex beams, and improve spectrum utilization.

[0079] (3) Potential for multi-scenario applications: This phase plate is not only suitable for the communication field, but can also be used in radar, high-resolution imaging, energy transmission and other scenarios, showing its wide application potential in the field of electromagnetic control.

[0080] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be understood as a limitation to the invention.

[0081] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "example," "specific example," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example.

[0082] Obviously, the described embodiments are only some of the embodiments of the present application, rather than all of the embodiments. Mentioning "embodiment" in this article means that the specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present embodiment application. The appearance of this phrase in various positions in the specification does not necessarily mean that they are all the same embodiments, nor are they independent or alternative embodiments that are mutually exclusive with other embodiments. It can be understood explicitly and implicitly by those skilled in the art that the embodiments described herein can be combined with other embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of this application.

[0083] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the claims and their equivalents.

Claims

1. A terahertz vortex phase plate based on a dual-band staggered metasurface, characterized in that: The metasurface is composed of a plurality of periodically arranged metasurface units (10), each of which comprises, from top to bottom, a metal structure layer (100), an intermediate dielectric layer (200), and a metal reflective layer (300); wherein the metal structure layer (100) comprises: Two concentrically arranged metal split rings are configured to generate vortex beams with different topological charges at different frequencies by controlling the rotation angles of the two metal split rings respectively, and to control the phase at different frequency bands based on a single rotation of each metal split ring by regulating the electromagnetic coupling between the two metal split rings. The metal split rings include: A first metal open ring (110) is provided on the intermediate dielectric layer (200), wherein the first metal open ring (110) has an opening angle ranging from 30° to 60°, an outer diameter ranging from 21 μm to 25 μm, and an inner diameter ranging from 16 μm to 20 μm; a second metal opening ring (120) arranged outside the first metal opening ring (110) and having the same center as the first metal opening ring (110); the second metal opening ring (120) has an opening angle ranging from 30° to 60°, an outer diameter ranging from 46 μm to 50 μm, and an inner diameter ranging from 41 μm to 45 μm; By controlling the rotation angles of the two metal split rings respectively, vortex beams with different topological charges at different frequencies are generated, specifically: When the first metal split ring (110) is rotated, a vortex beam with a topological charge of -1 is generated in the 1.35 THz frequency band; When the second metal open ring (120) is rotated, a vortex beam with a topological charge of 3 is generated in the 0.47 THz frequency band.

2. The terahertz vortex phase plate based on the dual-band staggered metasurface according to claim 1, characterized in that: The arrangement period of the metasurface unit (10) is p=110 μm to 120 μm, wherein: The thickness of the metal structural layer (100) and the metal reflective layer (300) are both not less than 0.2 μm; The thickness of the intermediate dielectric layer (200) ranges from 75 μm to 125 μm.

3. The terahertz vortex phase plate based on the dual-band staggered metasurface according to claim 1, characterized in that: In each metasurface unit (10), the centers of the two metal open rings and the geometric centers of the intermediate dielectric layer (200) and the metal reflective layer (300) are all located on the same vertical line.

4. The terahertz vortex phase plate based on the dual-band staggered metasurface according to claim 3, characterized in that: The intermediate dielectric layer (200) is polyimide, has a relative dielectric constant of 3.5, and a tangent loss in the range of 0.001 to 0.

005.

5. The terahertz vortex phase plate based on the dual-band staggered metasurface according to claim 1, characterized in that: The metal structural layer (100) and the metal reflective layer (300) are made of the same material.

6. The terahertz vortex phase plate based on the dual-band staggered metasurface according to claim 5, characterized in that: The material is any one of gold, silver, copper and aluminum.

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